Tremolo or vibrato devices for producing special effects on a guitar are well known in the prior art. In fact, various devices of this kind, having different structural configurations, are presently available in the marketplace. These devices allow a guitarist to provide a vibrato effect, that is, to alter the tone of the instrument by rapidly increasing or decreasing the string tension during play. This alteration in string tension is brought about by back and forth movement of the tremolo device by a hand lever that is capable of transmitting a substantial stretching force to the strings. This force, particularly under the most demanding playing conditions, leads to slight longitudinal slippage of the strings, and the subsequent failure of the guitar to return to the tuning which existed prior to the use of the tremolo device.
In the past, little attention has been paid to improving the string nut assembly for use with tremolo devices, either in terms of improving the holding ability or providing for quick release and readjustment. One device for securing the strings at the string nut location is disclosed in U.S. Pat. No. 4,171,661 to Rose. In this prior art patent, the conventional string nut is replaced by a special string nut assembly with a series of blocks held by single bolts or screws for clamping the strings of a guitar near the end of the guitar neck. Specifically, the Rose string nut assembly includes a series of rigid blocks, each block clamping a pair of strings on a U-shaped channel member by means of a single screw. The blocks overlie the strings and hold them in proper position within aligned V-shaped slots in outstanding edges of the U-shaped member when the screws are tightened; the strings being released for retuning the instrument when the screws are loosened.
The Rose nut assembly suffers from several serious drawbacks. In order to retune a guitar fitted with the Rose nut assembly, it is necessary to use a separate wrench or screwdriver to loosen the blocks and allow adjustment of the string tension. Such a time consuming and tedious operation is particularly inconvenient during a live performance. Additionally, the needed tools may not be available on stage or during a recording session when an audience and/or a highly paid sound technician is left sitting and waiting. Indeed, some guitar manufacturers have recognized this problem. However, they have attempted to solve it in a patchwork manner by attaching a tool holder to the back side of the peghead of the guitar. While the tool is then usually more convenient in such a holder, it is subject to be lost, or even fall out at the most inopportune times. Moreover, even when the tool is readily available, an inordinate amount of time is required to remove the tool, make the necessary adjustments, and return the tool to the holder.
Many of the above mentioned shortcomings of the prior art are overcome by the locking nut assembly disclosed in applicant's copending U.S. patent application Ser. No. 544,122, entitled Locking Nut Assembly For A Guitar. This last mentioned assembly includes a baseplate connected to a guitar neck near the peghead, which baseplate is also used in lieu of the more conventional string nut at the same location to separate and maintain the strings above the fretboard. The baseplate has an outstanding ridge with a series of spaced V-shaped slots for receiving individual strings of the instrument. A locking block is fitted on the baseplate to overlie the strings. When compressingly engaged by a cam action lock screw, the locking block applies a clamping pressure against the interposed strings, firmly and positively locking the strings against movement between the locking block and base plate.
The assembly disclosed in applicant's above identified copending patent application advantageously prevents string slippage on the guitar while the nut assembly is in a locked position. Hence, when a tremolo device is deactivated, the instrument returns to its original string tension and original tuning. Further, such an assembly is easily and rapidly moved, without tools, to an unlocked position to allow free movement of the strings for retuning the instrument. However, when it is desired to retrofit a conventional guitar, it is necessary to remove the original string nut to secure the locking nut assembly. The difficulties involved in removing an original string nut from a guitar have caused many guitarists to defer any such reconstruction to professional craftsmen or discouraged the use of tremolo devices altogether. Further, the V-shaped slots of both the prior art assemblies and applicant's above-described assembly accommodate only an extremely limited range of string spacings, and the V-shaped slots of such assemblies must be carefully coordinated and matched with the string spacings of a particular guitar.
Thus, even with the substantial improvements offered by the assembly of applicant's copending application, there is a strong need for a string locking assembly to retrofit existing string instruments without the necessity for reconstruction of the string nut. Further, there is a need for a more universal string locking assembly which is usable upon a variety of instruments having a wide range of string width spacings.